Occlusion catheter having compliant balloon for use with complex vasculature

ABSTRACT

A catheter used for treatment of complex vasculature, such as a bifurcated aneurysm, is provided with an inflatable balloon at a distal portion thereof. The shape, location and material of the inflatable balloon are selected such that when inflated, the balloon conforms to the shape of the complex vasculature, or at least a portion thereof, without appreciably deforming the vessel walls. In this manner, the balloon can be used to control flow in the vasculature, for example occluding a selected branch of the vasculature during introduction of material in order concentrate the material and minimize its disbursement by blood flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.provisional applications Ser. Nos. 60/317,232 and 60/318,215, filed Sep.4, 2001, and Sep. 7, 2001, respectively, the entire contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention is directed to balloon catheters used in the treatment ofaneurysms and other vascular diseases in a mammalian patient.

References

The following publications are cited in this application as superscriptnumbers:

¹ Castaneda-Zuniga, et al., Interventional Radiology, in VascularEmbolotherapy, Part 1, 1:9-32, Williams & Wilkins, Publishers (1992)

² Greff, et al., Compositions for Use in Embolizing Blood Vessels, U.S.Pat. No. 5,667,767, issued Sep. 16, 1997

³ Evans, et al., Cellulose Diacetate Compositions for Use in EmbolizingBlood Vessels, U.S. Pat. No. 5,580,568, issued Dec. 3, 1996

⁴ Evans, et al., Novel Embolizing Compositions, U.S. Pat. No. 5,695,480,issued Dec. 9, 1997

⁵ Jones, et al., Methods for Embolizing Vascular Sites with anEmbolizing Composition Comprising Dimethylsulfoxide, U.S. Pat. No.5,830,178, issued Nov. 3, 1998

⁶ Whalen, et al., Novel Embolizing Compositions Comprising High PolymerConcentrations, U.S. patent application Ser. No. 09/574,379, filed May19, 2000

⁷ Evans, et al., Methods for Embolizing Blood Vessels, U.S. Pat. No.5,702,361, issued Dec. 30, 1997

⁸ Evans, et al., Methods for Embolizing Blood Vessels, U.S. Pat. No.6,017,977, issued Jan. 25, 2000

⁹ Wallace, et al., Intracranial Stent and Method of Use, U.S. Pat. No.6,007,573, issued Dec. 28, 1999.

¹⁰ Racchini, et al., Porous Balloon For Selective Dilation and DrugDelivery, U.S. Pat. No. 5,458,568, issued Oct. 17, 1995

¹¹ Whalen, et al., Novel High Viscosity Embolizing Compositions, U.S.patent application Ser. No. 09/574,379, May 19, 2000

¹² Szikora, et al., Endovascular Treatment of Experimental Aneurysmswith Liquid Polymers: The Protective Potential of Stents, Neurosurgery,38(2):339-347 (1996)

¹³ Kinugasa, et al., Direct Thrombosis of Aneurysms with CelluloseAcetate Polymer, Part II—Preliminary Clinical Experience, J. Neurosurg.,77:501-507 (1992)

¹⁴ Kinugasa, et al., Cellulose Acetate Polymer Thrombosis for theemergency Treatment of Aneurysms: Angiographic Finding, ClinicalExperience, and Histopathological Study, Neurosurgery, 34:694-701 (1994)

¹⁵ Mandai, et al., Direct Thrombosis of Aneurysms with Cellulose AcetatePolymer.: Part I—Results of Thrombosis in Experimental Aneurysms, J.Neurosurg., 77:497-500 (1992)

¹⁶ Talia, et al., Bioabsorbable and Biodegradable Stents in Urology, J.Endourology, 11(6):391 (1997)

¹⁷ Wallace, et al., Intracranial Stent and Method of Use (DeliverySystem), U.S. application Ser. No. 08/762,110 (pending application).

All of the above references are herein incorporated by reference intheir entirety to the same extent as if each individual reference wasspecifically and individually indicated to be incorporated herein byreference in its entirety.

State of the Art

Aneurysms arise in mammalian subjects and, in particular, human subjectsas a result of vascular disease wherein the arterial wall weakens and,under pressure due to blood flow, the arterial wall “balloons.”Continued growth and/or eventual rupture of the ballooned arterial wallis associated with high morbidity and mortality rates. Intracranialaneurysms are of particular concern because surgical procedures to treatthese aneurysms before rupture are often not feasible and furtherbecause rupture of these aneurysms can have devastating results on thepatient even if the patient survives rupture. Accordingly, treatmentprotocols for intracranial aneurysms may be prophylactic in nature,i.e., to inhibit rupture or rerupture of the aneurysm rather than toinhibit bleeding from the ruptured aneurysm.

Methods well documented in the art to inhibit intracranial aneurysmalrupture/bleeding include the delivery into the aneurysmal sac ofnon-particulate agents such as metal coils which are designed to inducethrombosis after delivery to the aneurysm, thereby inhibiting blood flowinto the aneurysm¹; delivery of a fluid composition into the aneurysmalsac which composition solidifies in the sac to inhibit blood flow intothe aneurysm²⁻⁶; or a delivery of a combination of non-particulateagents and a fluidic composition into the aneurysmal sac to inhibitblood flow into the aneurysm.⁷⁻⁸

In each case, the cranial aneurysm is treated by filling the aneurysmalsac in a manner which inhibits blood flow into the sac. This reducedblood flow correlates to reductions in aneurysmal stress and, hence, areduction in the likelihood of rupture. However, care must be taken toensure against migration of non-particulate agents or fluid compositionbeyond the aneurysmal sac (which can occur, for example, by overfillingof the sac) because this can result in parent artery or distalembolization which, in turn, has its own high level of morbidityassociated therewith.¹²

One method of containing the embolizing agent in the aneurysmal sacinvolves the use of a catheter having an occlusion or attenuationballoon. The catheter, and, specifically, the occlusion/attenuationballoon provided at the distal end thereof, performs the dual functionsof blocking or impeding flow in the vessel during treatment, such thatembolizing agent migration potential is significantly reduced, andproviding a sealing wall or harrier against the neck of the aneurysmalsac, which aids in retaining the embolizing agent within the sac duringits introduction.

Because the aneurysmal sac is usually associated with diseased tissuewhose structural integrity is therefore compromised, it is important tominimize the exertion of pressure against the vessel. The occlusionballoon, therefore, must be designed to provide proper support againstthe vessel, conforming to the shape of the vessel and providing thenecessary functionality associated with its use, without undulystressing the tissue, In simple cases, wherein the aneurysmal sac isnon-bifurcated and is located in a symmetrical, substantiallyconstant-diameter vessel, this is readily accomplished with conventionalballoon designs. However, in inure complex vasculature, for examplebifurcated, multi-branched or varying-diameter vessels, conventionaldesigns are confronted with challenges which they do not satisfactorilymeet. Specifically, these conventional designs utilize balloons, which,when inflated to the limits of safe operation—that is, to levels whichdo not impart unsustainable tissue deformation—fail to fully conform tothe complex vessel shape, and, accordingly, fail to provide the properamount of flow impedance or occlusion and support against the outflow ofembolizing agent during treatment.

BRIEF SUMMARY OF THE INVENTION

In accordance with the invention a microcatheter suitable for temporaryvascular occlusion is provided. The microcatheter includes asubstantially tubular structure with at least one lumen, and a balloonlocated at the distal portion of the tubular structure and in fluidcommunication with the lumen. The balloon is designed to deform at apressure which is less than the pressure required to deform the vascularwall when placed into a blood vessel.

Further in accordance with the invention, a method for treating ananeurysm in a mammal is provided, wherein the method includesidentifying an aneurysm in the mammal, and providing a cathetercomprising a substantially tubular structure with at least one lumen anda vascular balloon located at the distal portion of the tubularstructure and in fluid communication with the lumen, wherein the balloondeforms at a pressure less than the pressure required to deform thevascular wall in the vicinity of the aneurysm. The catheter is insertedinto the blood vessel associated with the aneurysm, wherein the distalportion of said catheter is located at a position such that uponexpansion of said balloon blood flow into the aneurysm is eitherattenuated and/or diverted prior to deformation of the vascular wall. Anembolizing agent is delivered into the aneurysm to inhibits blood flowinto said aneurysm.

Further in accordance with the invention, a catheter suitable fortreating an aneurysm in a vascular wall is provided. The catheterincludes a substantially tubular structure having at least one lumen,and an inflatable balloon located at a distal portion of the tubularstructure and in fluid communication with the lumen, wherein at least aportion of the inflatable balloon comprises a material which deforms ata pressure which is less than the pressure required to deform thevascular wall containing the aneurysm.

Further in accordance with the invention, a method for treating ananeurysm formed in the vascular wall of a mammalian patient is provided,the aneurysm being formed in the vicinity of at least one lumen definedby a blood vessel associated with the aneurysm. The method includesidentifying an aneurysm in the mammalian patient, introducing a ballooninto the vicinity of the aneurysm, the balloon being provided on acatheter which comprises a substantially tubular structure having atleast one lumen in communication with the balloon, at least a portion ofthe balloon comprising a material which deforms at a pressure which isless than the pressure required to deform the vascular wall in which thebifurcated aneurysm is formed, inflating the balloon such that bloodflow into the aneurysm is attenuated and/or diverted prior to undesiredcompression of the vascular wall, and delivering into the aneurysm anembolizing agent which inhibits blood flow into said aneurysm.

Further in accordance with the invention, a catheter suitable for use ina complex vessel is provided. The catheter includes a substantiallytubular structure having at least one lumen, and an inflatable balloonlocated at a distal portion of the tubular structure and in fluidcommunication with the lumen, wherein at least a portion of theinflatable balloon comprises a material which, when the balloon isinflated, conforms to the shape of the vessel for a sufficient length ofthe vessel to attenuate and/or occlude blood flow therein withoutsignificantly deforming the vessel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a diagrammatical view of the use of the catheter in accordancewith the invention during an embolization procedure;

FIG. 2 is a perspective view of a distal portion of a catheter inaccordance with the invention; and

FIGS. 3A and 3B are cross-sectional views of concentric (FIG. 3A) andnon-concentric (FIG. 3B) lumen arrangements of catheters in accordancewith the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically shows an occlusion catheter 10 in use in thetreatment of an aneurysmal sac 12 in accordance with the invention.Blood vessel 14 is complex in shape and structure and is shown as havinga main portion A, and as bifurcating into two branches B and C. It willbe appreciated that more complex vessel structures, including thosehaving varying diameters, or those having more than two branches,originating from the same or different locations relative to the mainportion, can be treated in accordance with the methods and devices ofthe invention without departure from. the spirit or scope of theinvention. Blood vessel 14 is a neurological vessel, in accordance withthe preferred application of the teachings of the invention.

Also shown in FIG. 1 is an injection catheter 16, depicted in positionduring treatment of aneurysmal sac 12. Catheter 16 is a separatecatheter from catheter 10 and is used to introduce an embolizing agent18 into the aneurysmal sac 12. The embolizing agent may be a one or morecoils (not shown), or it may be a fluid composition, preferablycomprising either a biocompatible polymer or a biocompatible prepolymer,but can also be a combination of coils with a fluid composition, asdescribed by Evans⁷⁻⁸. When a biocompatible polymer is employed, thefluid composition preferably comprises a biocompatible polymer, andoptionally a biocompatible contrast agent, and a biocompatible solventwhich solubilizes the biocompatible polymer wherein sufficient amountsof the polymer are employed in the composition such that, upon deliveryto the aneurysm, a polymer precipitate forms which fills at least aportion of the aneurysmal sac thereby inhibiting blood flow therein.Preferably, the viscosity of the polymer composition is at least about150 cSt at 40° C.

Such polymer composition can comprise, for example, a biocompatiblepolymer at a concentration of from about 2 to 50 weight percent; abiocompatible contrast agent at a concentration of from about 10 toabout 40 weight percent; and a biocompatible solvent from about 10 to 88weight percent wherein the weight percent of the biocompatible polymer,contrast agent and biocompatible solvent is based on the total weight ofthe complete composition.

Preferably, in this particular composition, the concentration of thepolymer ranges from 6 to 50 weight percent and more preferably 8 to 30weight percent.

Preferably, the polymer composition has a viscosity of at least about150, preferably at least about 200 and more preferably at least 500 cStat 40° C. More preferably the viscosity ranges from about 200 to 40,000cSt at 40° C., more preferably from about 500 to 40,000 cSt at 40° C.The viscosity can also range from about 500 to 5000 cSt at 40° C.

In another aspect of the invention, the biocompatible polymer can bereplaced with a biocompatible prepolymer and, when so used, the presenceof the biocompatible solvent becomes optional. In a further preferredembodiment, the biocompatible solvent is dimethylsulfoxide (DMSO),ethanol, ethyl lactate or acetone.

The term “biocompatible polymer” refers to polymers which, in theamounts employed, are non-toxic and substantially non-immunogenic whenused internally in the patient and which are substantially insoluble inthe body fluid of the mammal.

The biocompatible polymer is preferably non-biodegradable. Suitablenon-biodegradable biocompatible polymers include, by way of example,cellulose acetates²⁻⁶ (including cellulose diacetate), ethylene vinylalcohol copolymers, hydrogels (e.g., acrylics), polyacrylonitrile,polyvinylacetate, cellulose acetate butyrate, nitrocellulose, copolymersof urethane/carbonate, copolymers of styrene/maleic acid, and mixturesthereof.

Preferably, the biocompatible polymer employed does not cause an adverseinflammatory reaction when employed in vivo. The particularbiocompatible polymer employed is selected relative to the viscosity ofthe resulting polymer solution, the solubility of the biocompatiblepolymer in the biocompatible solvent, and the like. For example, theselected biocompatible polymer should be soluble in the amounts employedin the selected biocompatible solvent and the resulting compositionshould have a viscosity suitable for in vivo delivery by, e.g.,injection, or by screw-assisted syringe delivery. Such factors are wellwithin the skill of the art.

Preferred biocompatible polymers include cellulose diacetate andethylene vinyl alcohol copolymer.

Cellulose diacetate polymers are either commercially available or can beprepared by art recognized procedures.

Ethylene vinyl alcohol copolymers comprise residues of both ethylene andvinyl alcohol monomers. Small amounts (e.g., less than 5 mole percent)of additional monomers can be included in the polymer structure orgrafted thereon provided such additional monomers do not alter theproperties of the composition. Such additional monomers include, by wayof example only, maleic anhydride, styrene, propylene, acrylic acid,vinyl acetate and the like.

The term “contrast agent” refers to a biocompatible radiopaque materialcapable of being monitored during injection into a mammalian subject by,for example, radiography. The contrast agent can be either water solubleor water insoluble and preferably does not contain radioactivity abovethe native or endogenous amounts naturally occurring in the elementsemployed (i.e., are “non-radioactive”).

Examples of water soluble contrast agents include metrizamide,iopamidol, iothalamate sodium, iohexol, iodomide sodium, and meglumine.Examples of water insoluble contrast agents include tantalum, tantalumoxide, and barium sulfate, each of which is commercially available inthe proper form for in vivo use including a preferred particle size ofabout 10 μm or less. Other water insoluble contrast agents include gold,tungsten, and platinum powders.

Preferably, the contrast agent is water insoluble (i.e., has a watersolubility of less than 0.01 mg/ml at 20° C.).

The term “biocompatible solvent” refers to an organic material liquid atleast at body temperature of the mammal in which the biocompatiblepolymer is soluble and, in the amounts used, is substantially non-toxic.Suitable biocompatible solvents include, by way of example,dimethylsulfoxide, analogues/homologues of dimethylsulfoxide, ethanol,acetone, ethyl. lactate, and the like. Aqueous mixtures with thebiocompatible solvent can also be employed provided that the amount ofwater employed is sufficiently small that the dissolved polymerprecipitates upon contact with the blood. Preferably, the biocompatiblesolvent is dimethylsulfoxide.

As seen from FIG. 1, catheter 10 is provided with a balloon 20 at adistal portion thereof. Balloon 20, shown in an inflated state, occupiesportions of the interior of main portion A, and branches B and C, ofvessel 14. In this mariner, balloon 20 occludes, or attenuates, flow invessel 14, such that embolizing agent 18 can be introduced intoaneurysmal sac 12 with minimal migration and loss. The size and materialof balloon 20, and the inflation pressure applied thereto, are selectedsuch that the balloon conforms to the irregular shape and structure ofvessel 14, and provides the necessary flow occlusion and/or attenuationto effectively apply embolizing agent 18, without appreciably deformingor stressing the vessel. Further, by such appropriate selection, balloon20 can provide an effective barrier against neck 22 of aneurysmal sac12, such that undesired outflow of embolizing agent 18 from theaneurysmal sac is reduced. All of these factors significantly contributeto the safety and efficacy of the embolization procedure.

FIG. 2 shows in greater detail the distal portion of catheter 10 of theinvention. The distal portion includes balloon 20, shown in a deflatedstate, and comprising a layer of flexible balloon material 26 defining achamber 28. Holes 30 provide fluid communication between chamber 28 anda central lumen 32 extending longitudinally within elongate, generallytubular body 34 of catheter 10.

The distal portion of catheter 10 is also provided with radiopaquemarker bands 36 and 38, which are retained in position around body 34 bycorresponding marker band retainers 36 a and 38 a. Retainers 36 a and 38a are preferably of a flexible material, such as plastic, which is heatshrunk over markers 36 and 38 during catheter fabrication. It will beappreciated that retainers 36 a and 38 a can alternatively be made of asingle, unitary component extending over markers 36 and 38, in whichcase it would be provided with holes in registry with holes 30 tofacilitate communication between chamber 28 and central lumen 32. Markerbands 36 and 38 may be of metallic or polymeric material, and mayalternatively be adhesively bonded in position, rather than usingretainers 36 a and 38 a.

Central lumen 32 is in fluid communication with a fluid reservoir (notshown) at the proximal end of catheter 10. Fluid (not shown) from thereservoir is selectively introduced into chamber 28, via holes 30, inorder to inflate balloon 20 during operation. The fluid may be salineand/or a contrast agent injected by syringe (not shown).

In an alternative structure, the catheter is provided with more than onelumen, at least one of which is in communication with the exterior ofcatheter 10 at the distal portion of the catheter, such that materialcan be introduced into or removed from vessel 14, or such that in situmeasurements of various patient conditions, such as pressure, can beaccurately performed. Moreover, additional lumens may be provided toaccommodate a guidewire or a microcather in order to facilitateintroduction of the catheter to the target portion of the patient'svasculature, in accordance with known catheterization techniques. Lumen32 can be adapted for this purpose, such that lumen 32 can serve themultiple purposes of accommodating a guidewire and providing inflationfluid to balloon 20. The multiple lumens can be concentric, or they canextend along different portions of the catheter, as seen from FIGS. 3Aand 3B, respectively showing cross-sectional views of multiple lumens40, 42 and 46, 47 in concentric and non-concentric arrangements incatheters 44 and 48 in accordance with the invention.

Balloon material 26 is selected to be flexible, such that balloon 20,when inflated, is very compliant. Preferably, material 26 is of acomposition which is based on styrenic olefinic rubber and hydrogenatedisoprene, such as that sold under the trade name ChronoPrene™, availablefrom CT Biomaterials, a division of CardioTech International, Inc.ChronoPrene™ includes the additives polypropylene as a reinforcingagent, and mineral oil as a plasticizer and processing agent. Balloonmaterial 26 is sterilizable and biocompatible, and is compatible withthe materials used during the embolization process. In particular, it iscompatible with solvents (for example dimethylsulfoxide (DMSO)),polymers, prepolymers and other materials involved in the embolizationprocess. The contemplated thickness of the balloon material 26 is in therange of about 0.004 inches to about 0.006 inches, and is preferablyabout 0.005 inches.

The characteristics of balloon material 26—including its material,shape, size and the manner in which it is formed and applied relative totubular body 34—are selected such that balloon 20, when inflated,readily takes the path of least resistance within the blood vessel, andminimally impacts the shape and integrity of the compromised tissue.This reduces the threat of rupture, and of subsequent stenosis. At thesame time, the functionally of the balloon is unhindered—that is, theballoon serves to effectively occlude or impede blood flow, or, in somesituations, divert it from an existing flow pattern in a bifurcated,complex vessel in a controlled, safe and reliable manner. The balloon20, or at least a portion thereof, will thus be more deformable than thevascular wall in the vicinity of the aneurysmal sac, even when thatvascular wall is diseased and is of compromised strength and stiffness.The balloon 20, or portions thereof, however, will remain sufficientlyrigid during operation so as not to appreciably penetrate into theopening, or neck, of the aneurysmal sac, even in situations where theneck of the aneurysmal sack is larger than the opening of a branch ofthe bifurcated vessel.

Factors to consider in providing the necessary balloon performance aremodulus and tensile strength of balloon material 26. A modulus at 300%,having a value less than about 300 psi and/or a tensile strength ofabout 600 psi, is preferred. ChronoPrene™ 15A can be used, which has aHardness-Shore A ASTM D2240 (3 sec.) rating of about 15, a specificgravity of about 0.89, tensile strength of about 600 psi, and elongationof greater than about 1,000%. Alternatively, ChronoPrene™ 40A can beused, which has a Hardness-Shore A ASTM D2240 (3 sec.) rating of about40, a specific gravity of about 0.90, tensile strength of about 700 psi,and elongation of about 500%. The material 26 may be pre-stretched orotherwise mechanically and/or thermally manipulated to improveperformance.

In forming balloon 20, material 26 can be shaped into a tubular form andsubjected to pre-treatment, which may include stretching and heating andannealing. The tube can then be bonded to tubular body 34. Bonding ispreferably effected using adhesives, or using heat treatment, forexample using laser, direct contact heat application, or forced airheating. Bonding can also be effected ultrasonically, or by RF (radiofrequency) welding, or mechanically swaging or pinching, or by othertechniques. In this manner material 26 is sealed against tubular body34, or against retainers 36 a and 38 a, at regions 50 and 52, such thatfluid-tight chamber 28 is achieved.

Designing the balloon 20 to be relatively large in length willcompensate for any shortcomings arising from its relative softness andcompliancy, and its low impact design. Larger size, in terms of thediameter of the balloon 20 when inflated and in terms of the overalllength of the balloon is contemplated. A preferred balloon length rangeis about 4 mm to about 30 mm, and a more preferred balloon length rangeis about 7 mm to about 20 mm. A preferred balloon diameter range isabout 1.5 mm to about 10 mm, and a more preferred balloon diameter rangeis about 3 mm to about 7 mm. A preferred length-to-diameter ratio rangeis about 0.5:1 to about 5:1. In this manner the balloon will effectivelyocclude/impede blood flow due to its large size, and particularly, largesurface area, and will not need to rely on forming a tight seal over asmall contact area with the blood vessel. Thus minimal stress is exertedagainst the vessel.

Balloon 20 is constructed such that an inflation pressure of about 200mmHg, or about 3/10 atmosphere, will provide the necessary volume andforce for proper operation. Such pressure will thus be slightly greaterthan systolic pressure, and will be just sufficient to inflate balloon20 without causing appreciable deformation of the vessel. Accordingly,damage to the vessel tissue is minimized. It is however contemplatedthat pressures to about 600 mmHg are possible. Application of embolizingagent can take place when the vessel and aneurysmal sac are in theirtrue shape and form, uninfluenced by straightening or mis-shapingforces. This will ensure that the introduced material is retained inplace, without imparting prolonged stress to the region. Acceptableperformance using ChronoPrene™ 15A has been realized, althoughChronoPrene™ in the range of 5A to 25A can also be used.

It is also contemplated that balloon 20 is predisposed to take oncertain irregular shapes matching those of the vasculature in which itis to be introduced. The balloon thus can be provided with nodules, orpre-stretched or pre-oriented during fabrication to take an theseirregular shapes, for example to bulge or self-position in a particulardirection, as seen in FIG. 1, with balloon 20 bulging to the left, intobranch B of vessel 14.

The distal portion of catheter 10 is preferably relatively flexible inorder to facilitate introduction of the catheter into tortuousvasculature. Other portions of catheter 10, however, may be relativelystiffer, in order to increase column strength and enhance pushability,thereby further facilitating control of the catheter. Relative stiffnessmay be achieved in a variety of ways, including suitable materialselection, reinforcement, and so forth.

While described in the context of embolization procedures, it will beappreciated that the catheter and method of the invention are generallyuseful for occluding and/or impeding flow in any vasculature whosestructural integrity has been compromised, since the invention involvesminimal pressure and exertion of force against the vascular tissue, andwill therefore not exacerbate the condition of the vessel.

The above are exemplary modes of carrying out the invention and are notintended to be limiting. It will be apparent to those of ordinary skillin the art that modifications thereto can be made without departure fromthe spirit and scope of the invention as set forth in the followingclaims.

1-58. (canceled)
 59. A microcatheter suitable for temporary vascularocclusion comprising: a substantially tubular structure with at leastone lumen and an inflatable balloon, the inflatable balloon located atthe distal portion of said tubular structure and positioned in fluidcommunication with said at least one lumen, said inflatable balloonbeing inflatable to an inflated state in which said inflatable balloondeforms at a pressure less than the pressure required to deform thevascular wall when placed into a blood vessel, said inflatable balloondimensioned to occlude vasculature in said inflated state; and one ormore radiopaque marker bands disposed in the vicinity of the inflatableballoon.
 60. The microcatheter of claim 59, wherein the at least onelumen is adapted to accommodate a guidewire.
 61. The microcatheter ofclaim 59, wherein the balloon is formed of a material that has a modulusat about 300% having a value less than about 300 psi and/or a tensilestrength of about 600 psi.
 62. The microcatheter of claim 59, whereinthe balloon is formed of a material that has a Hardness-Shore A ASTMD2240 (3 sec.) rating of about 15, a specific gravity of about 0.89,tensile strength of about 600 psi, and elongation of greater than about1,000%.
 63. The microcatheter of claim 59, wherein the balloon is formedof a material that has a Hardness-Shore A ASTM D2240 (3 sec.) rating ofabout 40, a specific gravity of about 0.90, tensile strength of about700 psi, and elongation of about 500%.
 64. The microcatheter of claim59, wherein the balloon is formed of a material that is pre-stretched,preoriented or otherwise mechanically and/or thermally manipulated suchthat the balloon assumes an irregular shape when inflated.
 65. Themicrocatheter of claim 59, wherein the thickness of the balloon is about0.004 inches to about 0.006 inches.
 66. The microcatheter of claim 59,wherein the thickness of the balloon is about 0.005 inches.
 67. Themicrocatheter of claim 59, wherein the length of the balloon is about 4mm to about 30 mm.
 68. The microcatheter of claim 59, wherein the lengthof the balloon is about 7 mm to about 20 mm.
 69. The microcatheter ofclaim 59, wherein the diameter of the balloon is about 1.5 mm to about10 mm.
 70. The microcatheter of claim 59, wherein the diameter of theballoon is about 3 mm to about 7 mm.
 71. The microcatheter of claim 59,wherein the length-to-diameter ratio of the balloon is about 0.5:1 toabout 5:1.
 72. The microcatheter of claim 59, wherein the balloon isinflatable at a pressure which is slightly greater than systolicpressure.
 73. The microcatheter of claim 59, wherein the balloon isinflatable at a pressure of about 200 mmHg.
 74. The microcatheter ofclaim 59, wherein the balloon is inflatable at a pressure of about 600mmHg.
 75. The microcatheter of claim 59, wherein the substantiallytubular structure includes multiple lumens.
 76. The microcatheter ofclaim 75, wherein the substantially tubular structure includesconcentric lumens.
 77. A catheter suitable for use in a complex vesselcomprising: a substantially tubular structure having at least one lumen;a single compliant inflatable balloon located at a distal portion ofsaid tubular structure and in fluid communication with said lumen; andone or more radiopaque marker bands disposed in the vicinity of theinflatable balloon; wherein at least a portion of said inflatableballoon comprises a material which is is pre-stretched or mechanicallyor thermally manipulated during fabrication to take on the irregularshapes matching those of a vessel to which it is to be introduced;wherein when the balloon is inflated, the balloon conforms to the shapeof the vessel for a sufficient length of the vessel to attenuate and/orocclude blood flow therein; and wherein the balloon does notsignificantly deform the vessel when fully inflated.
 78. The catheter ofclaim 77, wherein the material of the inflatable balloon comprisesstyrenic olefinic rubber and hydrogenated isoprene.